1 Cf. D. M. Armstrong, A Materialist Theory of Mind (London, 1968), Chapter 9; 'A Causal Theory of Knowledge' by Alvin I. Goldman, The Journal of Philosophy , Vol. LXIV, No. 12, June 22, 1967. A striking parallelism would appear to exist between 'the causal theory of knowledge' and the orthodox Stoic doctrine regarding the kataleptike phantasia . See, for example, Sextus Empiricus, Adversus Mathematicos 7.248 (reprinted in Stoicorum Veterum Fragmenta , edited by H. F. A. von Arnim, Leipzig, 1921, Volume I, page 18, 59C): 'An apprehensive appearance is one which has been stamped and sealed by the actual, and in accordance with the actual thing itself, in such a way that it would not be produced by what is not (the) actual' (I am indebted for the wording of this somewhat controversial translation to my colleague Mr. M. B. Wallace). See the discussion and additional ref